I was just recently in Jo Anns and was checking to see how much their Warm and Natural batting was and noticed something called "Scrim" by Pellon. It is 100% cotton and can be quilted every 10" or less. Has anyone ever used this and what was the final look after washing the finished quilt?

Based on a lecture given in our quilt guild, Scrim is a very thin layer of a plastic-like stuff on one side of the batting. If you have a batting like this, the scrim side should be put towards the backing fabric. It works best when used in a wall hanging, as it provides extra support to make it hang straight and minimize curving around the corners.
The lecture was mainly focused on Quilter's Dream Cotton Batting, and I'm not familiar with the Pellon "Scrim," but I'd imagine it would be a similar concept.
However, I could be wrong.

I just looked on the Pellon website. Here's a quote from their FAQ section:
"Q: What is scrim binder?

A: Scrim binder is a thin sheet of polypropylene which is very much like a dryer sheet that is needle punched onto one or more sides of batting as it is processed. Not all scrim binders used today are alike. Legacy™ By Pellon batting uses only a very lightweight scrim. This adds strength and durability that is sought by machine workers yet allows softness and ease of stitch that everyone appreciates. Our scrim does not create heavy, dense and stiff results."http://www.pellonideas.com/category/55-faqs.aspx

warm and natural also has a scrim
scrims are not always plastic- in fact often are a fabric-like cheese cloth-either cotton or linen
it is just a netting for the fibers to be adhered to that keep the batting from pulling apart- making it possible to quilt further apart- batts without scrim generally need to be quilted quite densly- like every 2"-4"= and are best for hand quilting- batts with scrim are more difficult to hand quilt and are better suited to machine quilting- polyester and cotton batts can be found with scrim.

The batting you saw at JoAnn's is Pellon Legacy. The natural cotton with scrim is their version of Warm & Natural.

I haven't used it, but Pellon says it's thinner than W&N and is supposed to have a better drape. Thinner is not necessarily better in my book. I do know it's wider (96" vs 90" for W&N) and it's cheaper, at least at JoAnn's.

Some claim they like it because it doesn't have the flecks that W&N has (had), but W&N doesn't have flecks since they upgraded their cleaning process.